The topic for this special issue is "Biportal Endoscopic Approach to Spine." This approach has significantly advanced recently, and the purpose of this issue is to address and discuss the advanced biportal endoscopic spine approach. I sincerely thank the lead editors who have spearheaded the publication of this special issue: Don Young Park from the USA, Jwo-luen Pao from Taiwan, and Ji Yeon Kim, and Jae Won Jang from Korea.The biportal endoscopic approach was first introduced in 1996 by Dr. De Antoni [1,2]. However, biportal endoscopy did not advance significantly in the field of spinal surgery and was not commercially or clinically developed. Biportal endoscopy was introduced to South Korea and has made remarkable advancements since the 2010s [2,3]. Similar to conventional spine surgery, biportal endoscopic approaches were performed in the prone position, using a radiofrequency probe and a drill, and a surgical toolkit set was developed [3]. It further evolved in Korea under the name unilateral biportal endoscopy (UBE). UBE is the abbreviation for unilateral biportal endoscopy, but it is now commonly used as a representative term for biportal endoscopy [2]. Recently, UBE has been established as a globally practiced surgical technique [4][5][6].Currently, UBE is being performed not only in South Korea but also globally, experiencing rapid advancement [5,6]. It is used not only for simple decompressive surgery but also for interbody fusion [7]. Moreover, UBE is applied in the surgical treatment of not only lumbar conditions but also cervical and thoracic spine diseases [8][9][10]. In the lumbar region, UBE was first attempted for discectomy, and later, laminectomy was successfully performed using UBE to treat lumbar central or lateral recess stenosis [3]. If lumbar discectomy is considered the first generation of UBE, subsequent procedures such as lumbar laminotomy, paraspinal approach, and contralateral approach can be regarded as the second generation. More recently, lumbar interbody fusion has been performed using the UBE approach, marking it as the third generation of lumbar UBE surgery (Table 1) [4,11,12]. UBE surgery in the cervical and thoracic regions has been recently developed but is continuously advancing [9,13]. UBE is primarily utilized for surgeries involving posterior approaches in the cervical and thoracic spine. The UBE approach was first successfully applied in posterior cervical foraminotomy (PCF) [10]. Currently, it has also been successfully performed in decompressive cervical laminectomy for cervical spondylotic myelopathy [9]. Moreover, UBE is now being used in cervical laminoplasty and posterior cervical instrumentation, such as cervical 81 www.jmisst.org